Several major CRM companies have developed special pacemakers “IPGs” that allow for the delivery of resynchronization therapy. This technology uses atrial synchronized, biventricular pacing and requires placement of a lead in or on the right atrium as well as the right and left ventricles. Placement of a lead inside the left ventricle has not been clinically feasible to date due to dislodgement and the risk of embolism formation potentially leading to a stroke.
To answer the challenge of placing the left ventricle (LV) lead, considerable effort has gone into the development of special leads and delivery systems for placing the LV lead in a coronary vein. These leads are often referred to as coronary sinus (CS) leads, since the lead passes through the CS. CS leads have been challenging for the electrophysiologist to place and often require considerably more time and increased fluoroscopy exposure than traditional endovascular right side leads. Following implantation, the CS lead may dislodge in 10+% of patients leading to less than desirable performance. At least 10% of the target patients are not candidates for CS leads due to the anatomical structure of their coronary veins.
An alternative to CS leads is the use of epicardial or myocardial leads. Traditionally, these leads have been placed during open chest surgical procedures (sternotomy) or through a less traumatic subxiphiod or subcostal approach to the apex of the heart. The invasiveness of a full sternotomy would not be well tolerated by the CHF patients.
The placement of the lead on the apex of the heart is not desirable for resynchronization therapy. It is generally believed that the target location on the heart for resynchronization therapy is the lateral side of LV 2-3 cm apical of obtuse marginal and circumflex artery junction. Optimization of the target site may be achieved by ECG mapping of the heart to determine the location on the left ventricle that has the latest activation. Other epicardial locations that are normally accessible only with a sternotomy may be reached through the use of some embodiments the present invention in minimally invasive (MI) approaches.
To reach the target location through MI techniques, endoscopic ports and special endoscopic instruments may be employed. During a minimally invasive procedure it may be desirable to pass the device through a port. The port ID and length limit the amount of curvature that can preexist in an implant tool.
It is desirable for a lead to be implanted with the center axis of the helical electrode normal to the surface of the heart. The rigid prior art introducers often require a straight line between the point of entering the body and the implant position on the heart. This alignment is extremely challenging since the target spot is not directly visualized. Many or most traditional lead introducers are not suited for a MI approach due to their size and need for a straight-line approach. When leads must be placed on the superior portion of the left ventricle, as with resynchronization therapy, specialized tools and methods must be employed to reduce trauma to the patient and reach the appropriate location.
What would be desirable are devices and methods for placing epicardial-myocardial leads using minimally invasive techniques.